Blind rivet fastening apparatus

Abstract

A clutch apparatus for releasing the transmission of rotation from an electric motor to a spin shaft, is equipped with a rear clutch nut and a front clutch nut in order from the rear end side. The rear clutch nut transmits rotating force from the electric motor to the front clutch nut when engaged with the front clutch nut, but is disengaged from the front clutch nut by a predetermined rotation load. The front clutch nut has a cylindrical shape, so that the spin shaft can be arranged at an axial center portion, and when engaged with the engaging unit of the spin shaft, the rotating force is transmitted to the spin shaft, but the clutch is disengaged by a backward stroke of the front clutch nut and a predetermined stroke toward the tip of the spin shaft.

What is claimed is: 
     
       1. A fastening apparatus for fastening a blind nut to a member to be mounted, the fastening apparatus provided with a power transmission unit configured to transmit the rotation of an electric motor, the power transmission unit having a first transmission system and a second transmission system, the fastening apparatus comprising:
 a joint shaft that is arranged in front of the electric motor and is rotated by power transmitted by the first transmission system of the power transmission unit; 
 a spindle that is arranged in front of the electric motor and that is rotated by power transmitted by the second transmission system of the power transmission unit; 
 a spin shaft that grips a shaft unit of a mandrel and rotates the mandrel with rotation of the joint shaft; 
 a rotating clutch for transmitting the rotational force of the joint shaft to the spin shaft; and 
 a stroke clutch that is disposed between a stroke mechanism and the spindle, and that transmits the rotation of the spindle to the stroke mechanism, the stroke mechanism translating the mandrel with rotation of the spindle, wherein: 
 the rotating clutch is provided with a rear clutch nut and a front clutch nut arranged in front of the rear clutch nut; 
 the rear clutch nut transmits the rotational force of the joint shaft to the front clutch nut when engaged with the front clutch nut, but is disengaged from the front clutch nut by a predetermined rotational load; 
 the front clutch nut has a cylindrical shape so that the spin shaft can be arranged at an axial center portion of the front clutch nut, and the front clutch nut is configured so that when it is engaged with an engagement unit of the spin shaft, a rotational force is transmitted to the spin shaft, but the front clutch nut is disengaged from the spin shaft by a predetermined stroke shaft an axial direction; 
 the stroke clutch is provided with a spindle clutch and a nut clutch arranged in front of the spindle clutch; and 
 the spindle clutch transmits the rotational force of the spindle to the stroke mechanism when engaged with the nut clutch, but is disengaged from the nut clutch by a predetermined stroke rearward. 
 
     
     
       2. The fastening apparatus according to  claim 1 , wherein the stroke mechanism that translates the mandrel is provided with a cylindrical ball screw nut that rotates with the rotation of the spindle clutch and the nut clutch, and a ball screw shaft that is established at the center of the ball screw nut and moves in the axial direction with the rotation of the ball screw nut to translate the mandrel. 
     
     
       3. The fastening apparatus according to  claim 2 , further comprising a spin-pull head case that is arranged on the tip side of the ball screw shaft and moves in the same direction as the ball screw shaft with the stroke of the ball screw shaft, wherein when the spin-pull head case moves a predetermined distance in a rearward direction, it is fitted with a spin-pull head disposed on the front end side of the spin shaft, and moves so as to retract the mandrel together with the spin-pull head. 
     
     
       4. The fastening apparatus according to  claim 1 , further comprising a switch for starting the electric motor by pressing the mandrel in the axial direction, wherein when the tip of the mandrel is pressed rearward in a state in which the blind nut is disposed at the tip of the mandrel, the switch of the electric motor is closed by the rotational force from the electric motor, and the mandrel is rotated via the spin shaft engaged with the rotating clutch, and when the blind nut is mounted on the mandrel, the mandrel and the spin shaft are translated in a distal direction so that the spin shaft is disengaged from the rotation rotating clutch and the switch is opened, and in a state in which the spin shaft is disengaged from the rotating clutch, when the electric motor is started via a trigger by a user's operation, the spindle is rotated and the mandrel is translated in a rearward direction via the stroke mechanism so that the blind nut is fastened to the member to be mounted. 
     
     
       5. The fastening apparatus according to  claim 1 , wherein the rear clutch nut has a cylindrical unit, a flange unit at one end of the cylindrical unit, and a plurality of first fan-shaped portions formed on a front surface of the flange unit, the first fan-shaped portions having one end in a circumferential direction with a first vertical surface perpendicular to an end surface of the flange unit, the first fan-shaped portions having another end with a first inclined surface inclined with respect to the end surface of the flange unit, the first fan-shaped portions being configured to rotate integrally with the joint shaft, the front clutch nut having a plurality of second fan-shaped portions with a shape complementary to the first fan-shaped portions, the second fan-shaped portions having one end in the circumferential direction with a second vertical surface perpendicular to an end surface of the front clutch nut, the front clutch nut having another end with a second inclined surface inclined with respect to the end surface of the front clutch nut, the second vertical surface of the second fan-shaped portions of the front clutch nut being engageable with the first vertical surface of the first fan-shaped portions of the rear clutch nut the second inclined surface of the second fan-shaped portions of the front clutch nut being engageable with the first inclined surface of the first fan-shaped portions of the rear clutch nut the front clutch nut being configured to rotate integrally with the rear clutch nut. 
     
     
       6. The fastening apparatus according to  claim 5 ,
 wherein when the blind nut is mounted on the mandrel and the spin shaft cannot rotate, the first inclined surface of the first fan-shaped portions of the rear clutch nut slips with the second inclined surface of the second fan-shaped portions of the front clutch nut so that the rear clutch nut moves rearward. 
 
     
     
       7. The fastening apparatus according to  claim 1 ,
 wherein the engagement unit of the spin shaft has a plurality of small-diameter portions having a diameter smaller than a diameter of a columnar shape on a distal end side of the engagement unit, a rear end side of the engagement unit of the spin shaft has a diameter smaller than the diameter of the small-diameter portions of the engagement unit, and a cylindrical inner portion of the front clutch nut has a shape complementary to the engagement unit.